Experimental study on the control of temperature oscillation in power electronics via pulsating jet impingement

Abstract

Thermal oscillations in power electronics due to transient load conditions present a significant challenge. This experimental study investigates the application of intermittent jet impingement, coupled with transient heat flux boundary conditions of 100 W, 200 W, and 300 W, to a thermal test chip at a frequency of 0.5 Hz (70 % duty cycle), to assess its effectiveness in minimizing junction temperature fluctuations. Temperature oscillations were recorded to compare the advantages of intermittent pulsation over steady jet flow. The results demonstrate reduced hot spot temperature oscillations of 10 %, 12.5 %, and 16.7 % at 100 W, 200 W, and 300 W, respectively, at a Reynolds number of 8850. Remarkably, even during the pulsation off-period, the minimum temperature limit was maintained at the inlet temperature of the jet, attributed to the formation of strong vorticity rings at the end of the jet pulse, inducing a cooling effect and reducing the junction temperature. Pulsating jets exhibit superior control over temperature fluctuation compared to steady jets, with the reduction being more pronounced at Reynolds numbers closer to 2000 and diminishing as Reynolds number increases to 17000. Moreover, the heat transfer coefficient and the Nusselt number enhanced by 18 % due to pulsating jet impingement. An enhancement factor is introduced to quantify the benefits of using pulsating jets, revealing a higher reduction in temperature oscillation compared to steady jets at the same time-averaged Reynolds number, valid within the Reynolds number range of 2000–14000. Additionally, a correlation is proposed to calculate the enhancement factor for pulsating jets. Finally, the pulsating jet impingement proves to reduce the exergy destruction by 30 % compared to steady jet.